1. Field of the Invention
The present invention relates to wireless communication technology. It more particularly relates to a wireless communication device that alters its operating mode in accordance with the operating state of an electronic apparatus whereto it is bundled for the purpose of maintaining an omni-directional radiation pattern. The present invention allows a more stable and reliable wireless transmission capability by ensuring that the antenna device always operates with best transmission quality even though the apparatus may vary its physical orientation when being operative. Obviously, the present invention is most suitable for portable wireless communication systems without fixed physical locations and orientations, such as notebook computers having network interface cards, or wireless network access points.
2. Description of the Related Art
Antennas provide wireless communication functionality to mobile devices and have become key components in the mobile telecommunication field. An antenna is practically an arrangement of metal substances in accordance with the theory of electromagnetic (EM) fields known as Maxwell's equations such that a particular pattern of electromagnetic wave can be radiated or received. A practical antenna can be manufactured into different size and structure that satisfy the physical requirements of a particular usage, with different radiation pattern or receiving pattern. Usually an antenna radiates power or electromagnetic energy in such a way that the radiation intensity varies as a function of spatial direction. That is, the antenna does not radiate equal power in all directions. Therefore, to obtain higher gain and better transmission quality between two antennas fixed in space, it is desirable to orient and direct one antenna with the main lobe of its radiation pattern in which the maximum intensity lies pointing right to the other antenna. But for two antennas not installed in fixed locations, such as those bundled into notebook computers for mobile transmission, spatially orienting the antennas in advance is not useful for obtaining high radiation and reception quality because the mobile antennas will constantly change their relative physical positions.
For wireless transmission of mobile devices, one has to resort to antennas of omni-directional radiation pattern that radiate electromagnetic energy of substantially same intensity in all directions. Since two mobile devices communicating wirelessly with each other can be regarded for most of the time as lying in a horizontal plane, for practical reasons we only require that a mobile antenna is omni-directional in the horizontal plane.
FIG. 1 and FIG. 2 illustrate one solution for the above-mentioned orientation problem according to the prior art. A typical antenna 110 with omni-directional radiation pattern is incorporated into notebook computer 100 for wireless communication. The antenna 110 is omni-directional only in a plane making a specific angle with respect to its longitudinal structure. That is, the antenna has its main lobe lying on a predetermined plane relative to its physical conducting structure in which its radiation intensity is substantially equal in magnitude for all directions. In FIG. 1a, the antenna 110 is mounted on the side of the display panel 102, and is controlled by a wireless communication module 103. When the display panel 102 is open, the antenna 110 creates in the XY, or horizontal plane an omni-directional electromagnetic radiation pattern as illustrated in FIG. 1b. Because the antenna 110 is omni-directional, best performance in radiating electromagnetic signals to, or receiving from, all directions in the horizontal plane can be ensured even though the notebook computer 100 may rotate along Z-axis when being operative. In this way, the notebook computer 100 is able to wirelessly communicate with a device in all directions on the horizontal plane.
But in particular operating conditions wherein the display panel 102 is closed but the notebook computer 100 is still functioning as illustrated in FIG. 2a, the antenna 110 necessarily alters its physical orientation, which results in its horizontal radiation pattern being no longer omni-directional, but rather having significant drops of intensity value or nulls in particular directions as indicated in FIG. 2b. Under such circumstances, the probability that the notebook computer 100 experiences transmission malfunctions would be increased.
It is possible to have the antenna 110 installed in host 101 to avoid the orientation problem. But clustering the antenna 110 with other electronic components within host 101 necessarily amplifies electromagnetic interference there between and induces negative effects on the antenna 110.